Simulation of pore formation in lipid bilayers by mechanical stress and electric fields

Molecular dynamics simulations of pore formation and mem-brane rupture in phospholipid bilayers under mechanical andelectrical stress at an atomic level are presented. Pore formationcan be induced on a nanosecond time scale in simulations wherethe lateral pressure exceeds -200 bar or where an electric field of0.5 V/nm is applied across the membrane.Lipid bilayer membranes are remarkable structures consistingof two leaflets of phospholipids. Their mechanical properties arecentral to understanding the behavior of cell membranes. Forexample, the formation of transient water pores is believed tounderlie the passive transport of protons and hydrophilic compoundsthrough the bilayer. Pore formation is also relevant during processessuch as cell fusion and is important for drug release from liposomes.Experimentally, pores can be induced in membranes by applyingmechanical stress (i.e., pipet aspiration experiments) or an electricfield (electroporation). The precise mechanism by which pores formand their size, structure, and stability are, however, poorlyunderstood.